Formation of nickel-zinc ferrite embedded in a silica xerogel matrix

We report a study using X-ray diffraction, refinement Rietveld, IR absorption spectroscopy and vibrating sample magnetometry of the formation of particles of Ni-Zn ferrites embedded in a xerogel SiO2 matrix. Initial solutions were prepared mixing TEOS, distilled water, ethanol, and three different nitrates: iron, nickel and zinc. A molar ratio H2O:TEOS:Et-OH of 11.66:1.0:4.0 was used in all solutions. Formation of Ni0.5Zn0.5Fe2O4 as well as structural modifications of the SiO2 matrix induced by these particles are discussed. Ni-Zn crystals having dimensions varying from 4 to 16.5 nm have been synthesized by a suitable heat treatment schedule at temperatures varying from 700 to 1100degreesC. The coercivity values for different heat-treated samples are found in the range 11-193 Oe, which are significantly larger than those presented by bulk Ni-Zn ferrites.